Switching arrangement for automatic and semiautomatic telephone systems



Nov 10, 1931. G. DEAKlN ET AL 1,830,935

SWITCHING ARRANGEMENT FOR AUTOMATIC AND SEMIAUTOMATIC TELEPHONE SYSTEMS Filed June 15, 1929 '7 Sheets-Sheet l 1 2 (23%? H0 -FIG.2 I @1511 dllfl @JZLL 1L2; Sgr

gu'rl ELL-f 11% i mo 5%: Pin- 2o T 6- wi gw w 9; Q M A an-52 $1,. 1 'TL "i B L I ----12Ecr INVENTORS ATTORN EY NOV. 10, 1931. DEAKIN ET AL 1,830,935

SWITCHING ARRANGEMENT FOR AUTOMATIC AND SEMIAUTOMATIC TELEPHONE SYSTEMS Filed Jime 13, 1929 '7 Sheets-Sheet 2 FIG. 3

c. DEAKIN 'L. P'OLINKOWSKY INVENTORS ATTORN EY Nov. 10, 1931. GDEAKW AL 1,830,935

SWITCHING ARRANGEMENT FOR AUTOMATIC AND SEMIAUTOMATIC TELEPHONE SYSTEMS FIG. 6

a Finm MFR L J b i I FFrr L z. v i 0 r 1 5-0 w I fir .d 51 5M 1 5 v m I i a M I gg l i I I l l l i G. DEAKIN L POLINKOWSKY INVENTORS ATTORNEY Nov. 10, 1931.

SWITCHING ARRANGEMENT FOR AUTOMATIC AND SEMIAUTOMATIG TELEPHONE SYSTEMS G. DEAKIN ET AL Filed June 13, 1929- FIG.7

HHM P. l l 1 i 1 r "mmwgiwflg 7 Sheets-Sheet 4 Am; H

a 65mm L. POLINKOWSKY INVENTORS ATTORNEY NOV. 10, 1931. qb ET AL 1,830,935

SWITCHING ARRANGEMENT FOR AUTOMATIC AND SEMIAUTOMATIC TELEPHONE SYSTEMS Filed June 15. 1929 7 Sheets-Sheet 5 FIG. 9

'INVENTORS c. DEAKIN 1.. POLINKOWSKY BY mm ORNEY Nov. 10, 1931.

G. DEAKIN ET AL SWITCHING ARRANGEMENT FOR AUTOMATIC AND SEMIAUTOMATIC TELEPHONE'SYSTEMS FIG. IO

Filed Jur xe 15. 1929 '7 Sheets-Sheet 6 INVBITORS G. DEAKIN L. POLINKOWSKY BY .WM

ATTORNEY NOV. 10, 1931. DEAK|N T AL 1,830,935

SWITCHING ARRANGEMENT FOR AUTOMATIC AND SEMIAUTOMATIC TELEPHONE SYSTEMS Filed June 13. 1929 7 Sheets-Sheet 7 FIG.II

6. DEAKIN L. LINKO SKY l NVENTORS BY WM ATTORNEY Patented Nov. 10, 1931 UNITED 'sTATEs PATENT oFric GERALD DEAKIN, OE NEW YORK, N. Y., AND LIPA 2OLINKOWSKY, OF PARIS; FRANCE, ASSIGNORS TO INTERNATIONAL STANDARD ELECTRIC CORPORATION, OF NEW YORK, N. --Y.

SWITCHING ARRANGEMENT FOR AUTOMATTC AND SEMIAUTOMATIG TELEPHONE SYSTEMS Application filed June 13, 1929, Serial No. 370,673, and in Great Britain June 13, 1928.

a system in which at each numerical switching stage are employed single-motion conversation selectors controlled by control switches each common to a plurality of conversation selectors but individual to the switching stage to which said conversation selectors belong, a common controlswitch is set under the control of a register controller to which reve-rtive impulses are sent during the advance of said control switch to a selected position.

This and other features of the invention will be better understood from a consideration of the following description taken in conjunction with the accompanying drawings which illustrate one embodiment of the.

invention.

Referring now to the accompanying draw-' ings,

- circuit Fig. 1 shows a subscribers line and'starting circuit and a first lin'e finder Fig. 2 shows a second line finder common starting circuit arrangement Fig. 3 shows a second line finder circuit Fig. 4 shows a first group findercircuit Fig. 5 shows a second group finder circuit Fig. 6 shows a final finder circuit Fig. '7 shows a first group finder control When the tele hone is removed from the .1

switch hook at su station S the calling line is The subscriber dials in the usual way.

The first digit dialled advances the thousands register in the register circuit to the corresponding position. When the first digit has been received a signal is sent forward from the register circuit to cause the first group finder switch lGF associated with the line finder QLF to become connected with its associated control circuit, the finder switch IQ]? of which is set in rotation and hunts until it finds the first group finder switch lGF. The control finder 1013 is then further advanced to 'a position corresponding to the first digit dialled in which position it marks the wanted group of trunks outgoing from the bank of the switch lGF: During the last mentioned movement revertive impulses are sentback from the control finder ICF to 7 count out the thousands register switch in the register circuit BC. The first group finder lGF is now caused to hunt for a free trunk extending to a second group finder QGF the associated control circuit 20F ofwhich is idle in the group determined by the setting of control finder 10F.

It should be noted that the trunks from the arcs of the group finder switches need not be arranged. in any definite order and further the groups need not contain the same number of trunks. Whenever it is found necessary to increase the number of trunks in a particular group this can be done without disturbing the existing connections the additional trunks being connected to any spare positions in the arcs.

The further extension of the connection depends upon the type of call which is being set up. In the case of a normal call when the second digit has been dialled a signal is tached to its control circuit, the finder 2G3? switches are arran ed to continue of which is set in rotation and hunts until it finds the en a ed second group finder QGF. The control vanced to a position corresponding to the second digit dialled to mark a wanted cup of trunks in the bank of the finder 2G1 durin this movement 'revertive im ulses g sent back to the register circuit G to count out the hundreds register switch therein. The second group finder 2GB is now caused to hunt in the wanted group for a free trunk to an idle final finder FF, the associated control circuit FCF of which is also idle. When the tens digit and at least one imulse of the units igit have been received y the register circuit BC the control circuit FQF is taken into use and its finder switch hunts until it picks up the final finder The control finder switch then advances further to a position corresponding to the tens digit, during this movement revertive impulses being sent back to count out the tens register. The final finder FF new advances to the wanted group after which the control finder switch continues to advance to a position corresponding to the wanted line: During this movement the final finder FF follows the control finder switch and a revertive impulse is sent-back to the units register for each position through which the control finder switch is advanced.

In addition to controlling the tons and units selection the final control circuit determines whether or not the called number is an individual line or a private branch exchange group. Provision is made for P. B. X. hunting by providinggthe cut-ofi relays of all the lines of a P. B. l group except the last line with an additional contact over which an engaged potential is applied to a corres ondmg terminal in the arc of the control der FCF when the line is busy. In case the called number corresponding to a P. B. X. group and the first line is found busy the control finder FCF causes the advance of the final finder FF until a free line is found. In case all the lines of the group are found busy the usual busy tone is transmitted to the calling party.

It should be noted that the control circuits are not engaged until the register circuit is ready to recelve the corresponding revertlve impulses. By this means the control circuits are held in use for the shortest possible time which has been found to average 1-3 seeonds (including restoring time) except when all the trunks of a. wanted group are found busy. In the latter case the grou -finder untin for a predetermine time, say 10 seconds. I

a free trunk is not found within this time the or QCF is then furtheredfinal finder switch and afterwards it controls the setting of this group or final finder switch.

.F or example there are usually 10 associated finder switches in a group served by one control circuit. If finder No. 6 has been selected aroma Ezeccding switching stage the control circult der advances and when position 6 is reached this group finder is attached. The control finder then continues. to advance and sends back the revertive impulses.

Ali the switches in the talking circuit are of the non-homing type and on release of the connection remain in the positions to which they were last set.

The register circuit RC is arranged to handle two di 't special service calls for which the num era 01, 02 etc... are reserved. Such calls are extended to an operators position over a regular first group finder such as M355 and a special second group finder such as SGF controlled by a control circuit SCF.

.The transmission bridge at the link circuit and the automatic subscriber cannot release lintll the operator breaks down the connec- =1on.

False calls are also automatically extended to afalse call operators position over two group selecting stages. The number 00 is assigned to false calls the register circuit being automatically set to these digits by grounded lines or failures to dial within 30 seconds. When a false call is extended the current bridge is automatically removed from the link circuit so as not to heat the bridge relay. The 0 erator by depressing a key can flasha guar lamp in the link circuit 2LF, lGF to indicate the finder which is held by the false call.

The system is designed to be built up in vertical bay units. The circuits on each unit will be completed in the factory, all exteriorabout to be described: The terminal strips'for exterior cabling are indicated T in this figure.

3o relay groups.

, Unit No. 1

' This unit comprises the subscribers line circuits, the first line finder circuits and the 5 final finder and final finder control circuits for a group of 100 lines. It is made up 'of two vertical bays the finder switches bemg mounted on one ha and the relay groups on the other. The nder switch bay has form example a capacity of 28,100-point finder switches which may be allotted as follows 14 first line finders; 12 final finders and 2 final control circuit finders. On the relay bay are mounted the line and cut-oil relays for the 15 hundred subscribers lines, the relays of the line finder circuits and the relays of the final I finder and final control circuits.

Unit N 0. 1A

This comprises a group of second line finders and associated relays.

Units N 0. 2A

Each of these units'compri'ses group finder circuits and control circuits and is assembled on one vertical 'bay with a capacity of, say 20,100-point group finder switches and two 50-point control circuit finder switches. On the same bay are mounted the associated Each group of 20 group finders is sub-divided into .two groups of 10 which are each served by one control finder circuit. The group finders are provided with 5 brushes. These units are used for the regular first group selecting stage and for the special service second group selecting stage.

Unit N 0. 2B This unit is similar to unit No. 2A but the 40 group finder switches are provided with 4 brushes only. These units are used for the regular second group selecting stage.

Unit No. 3

This unit comprises register circuitsand is made up of three vertical bays with a capacity of 16 register circuits which serve 100 line finder links. The 16 register finder switches and 16 time alarm switches are mounted on the centre bay of the unit. On

each of the two outside bays are mounted eight sets of digit switches and 8 sets of relays.

The switch racks may be made up in small units each provided with a driving motor and suitable means whereby the motor is only run when it is necessary to advance a switch of the unit: During busy hours provision may be made for running the motor continuously. A call will now be followed out in detail.

On a subscriber removing his receiver to make a'call the line relay L r, Fig. 1, is energized over the calling loop. Relay Lr places .65 a battery potential on the first line finder test multiple d and-e10 I a cireiiitiei 'a' 5 2 starting relay'Fsrw ich ener thef'aux-j iliary startingrel'ays Aer. Re ays Asr close circuits for the. clutchmagnets PF of all free first line finders in serieswith relay Lgr via contactsLhr2, Ltr 2. If 'thereare no free finders in the group relay Lgr remains de-energiz'ed and a guard lamp LGL lights.

When. a finder, say the one illustrated,

' reaches the calling line, test relay Ltr operates over its high-resistance right-hand winding, opens at contacts Ltr2 the circuit of magnet PF and at contacts Ltrl closes a circuit for relay "Lhr over its right-hand winding and the common start rela Car, Fi 2, of a sub-group of second line nders. Re ay Ltr also connects battery to the second line finder test multiple d. Relay Lhr at contacts Lhrl connects the low resistance lefthand winding of relay Ltr in parallel with its high-resistance winding to cause the relapse of relay F87" which de-energizes the relays A87 to arrest the other first line finders.

circuit switches, are for convenience shown in Fig. 2.

When a call is created from a first line finder circuit, the calling potential operates the Csr relay of the sub-group as already described and the latter relay over its front contact connects a ground to the armature of the over-change contact of the Ear relay, controlled by the particular control circuit which serves this group of group finders. If the control circuitis free relay Em" is de-energized and therefore relay Hsr becomes operated; the latter relay operates three other starting relays B81 in parallel, so closing the circuit for the 10 power magnets and for the high resistance windings of 10 test relays. It' is, of course, understood that only the finders which are free rotate.

The control of the high resistance windings of the test relays by the starting circuit is needed to avoid shunting out of the test pocr, lEar, 21301 of the control 7.

tential by the test relays of other sub-groups which may stay on the calling line; the latter test relays not having their windings grounded are not able to set up a call. If the control circu1t is engaged, the starting relays of the v sub-group will not be operated, because the front contact of relay Car is directed by the series of all the Al)? relays.

If the control circuit of the group is free, but all the line finders are engaged, the pilot relay Syr will notbecome operated when relay H81 is energized, and therefore slow-acting relay Ah) will operate and the following sub-group of starting relays will be operated in a similar way to when the control circuit itself is busy.

The group of the line finder circuits may not always be a perfect multiple of 10; therefore, the bottom starting scheme shown on the drawings is made to indicate how to connect the surplus finders of the group in the starting circuit.

There will exist in the exchange a control circuit, which may serve particularly the surplus group finders for all existing line finder groups. For the better understanding of the method, it is supposed that a complete group of line finder circuits is 52. The last subgroup of starting circuits may therefore serve 12 line finders instead of 10: the first 10 belonging to the normal control circuit and the remaining two belonging to the surplus control circuit. The relay 21302 of the latter control finder circuit controls another relay Earl with as many back contacts as there are groups of surplus group finders. Each back contact willcontrol one or two starting relays Hsrl, which close the circuits of the power magnets of the line finders and the high resistance winding of the test relays of the surplus line finder circuits.

The pilot relay 1891" is common to the 12 line finders, and this starting circuit operates as follows:

087 being operated, the latter relay operates the lHsr and Her-l relays provided the two control circuits are free; if the control circuit for the first 10 is engaged and the control circuit for the surplus finders is free, only the free surplus finders will rotate; or if the surplus control finder is engaged and the other control circuit is free, only the free finders outof the first 10 line finders will rotate.

it the control circuits are free, the pilot relay Sgr will operate as long as one of the 12 line finders is free, and in the caseof all being engaged, or the two controlcircuits being busy, relay lAbr will operate and the first sub-group of finders will be put in action the relay Her heingener ized over contacts or relays 108?, RAM an the group of the line finders comprises more than two surplus circuits, :lor example 6, the starting circuit may be split into two subgroups of 13 each, and not into a group or 10 and another group of 16, because it is not desirable to provide more than 13 finders common to one pilot relay, in order to avoid overheating ot the latter relay.

Assuming the. control circuit associated with the first sub-group of 2nd line finderlinks is free and that the second finder link comprising the second line finder, Fig. 3 and first group finder, Fig. 4, is also disengaged the driving magnet PL, Fig. 3 is energized terminal (Z of the finder to battery over co"- tacts Ltrl.

Relay 3A7" opens the circuit of magnet PL at contacts 3A1'1 and causes the energization of relay 3Gr from battery over contacts 311d,

Elli P2. Relay 301- at contacts 3071 connects the low-resistance right-hand winding of relay SA? to ground, causing the relapse of relay Csr, Fig. 2, provided there is no other call existing at this instant in the same group. Relay 3Cr also at contacts 3(11'2 closes a circuit for relay 3 57-, which operates slowly and over contacts BBrl, 3Gr4 and 3Fr6 energizes relayBDr. The time 3331 and 31)? take to operate covers the danger of a double test. Relay 3D?" closes a lockin circuit for relay 3=Cr via contacts 31011, 3.312, 3Cr3, and at contacts 3Dr2, 3Dr3, extends the a and Z) wires to the line relay 3Asr. ltelay 81% also energizes relay 8Hr which at contacts 3H1'2 grounds the 0 wire causing the energization of the cut-01f relay Cor, Fig. 1, over the left hand low-resistance winding of relay Lh'r' which remains operated over this circuit. Relay Cor disconnects the line relay Lr which opens the circuit of relay Ltr. Meanwhile relay Csr, Fig. 2, has de-energized and opened the circuits of relays Hsr, Bsr thereby stop ing further hunting.

Relay 3.173% 3614, 31-114 and locks up over contacts 3Ir3, 3Fr5, 3Gr4, 3B1'l. When relay 3AM operated it closed another circuit via contacts 3As1'2. for relay 3Br which being slow-to-release is maintained during dialling impulses.

Relay 311* at contact 3172 applies battery via contacts 3Cr5 to the leads 3 and 4 to energize the register starting circuit rela s Ar, Fig. 10 and to apply test potential to t e test contacts in the banks of the register finders.

ig. 3 is energized over contacts tery, over magnet PM, contacts E1 2, B14, T 1 t0 ound. The test relay T7 of the first fin er which reaches the calling line finder circuit energizes over its left-handhigh-resistance winding via contacts Dr1, normal contacts and brushes (1 of'a'll the di it registers to ground, opens the circuit o. magnet PM at contacts'Trl and at contacts T12 connects its low resistance winding in series with relay Shr to mark the link bu to other finders. Rela Shr which is of t e slow-release type an uards for double test, closes a circuit for re ayEr which closes a circuit over the primary winding of the tone coil TC, from battery, over' the windingof the magnet PM, contacts E13, G73, F1'2, to the dial tone lead D, and ap lies dial tone to the callin line over the ollowing circuit secondary winding of the tone transformer TC; small condenser MFl, contacts Rr6, windings of relay Pr, contact E16, register finder wiper b, contact 3Lr5, 3E1'3, Fig.3, wire brldge condenser, calling loop, a wire bridge condenser, contacts'3E1'1, 3174, register finder wiper a, Fig. 10, contact 1316 back to the tone transformer winding.

The calling part now dials the first or 4 thousands digit of t e wanted number, thereby intermittently opening the circuit of relay 3A1's, Fig. 3, which at each relapse closes an impulse circuit for relay Ir and Hr Fig. 10, via contacts 3As1-1, the finder brush d and contacts E14. At each energization of the impulse relay Hr a circuit is closed over contacts Hrl, J1-2 for the stepping ma et SW1 of the thousands digit register. elay 1r energizes on the first impulse and being of the slow-to-release type remains operated during impulsing. As soon as the thousands digit register reaches the first terminals set the following circuit is closed for relays 3E1', Fig. 3 and U1, Fig. 10 batter contacts 3D1-1, Fig. 3, -lower winding 0 relay 3E1', register finder brush a Fig. 10, contact F1 1, low resistance winding of relay Ur, brush 6 and firstterminal of first digit regis ter, contacts D73 to ground. A locking circuit for these relays is closed via contacts Url, Dr3. Relay U1 also closes a holding circuit for relay Er via contact Ur2.

Relay 3E1, Fig. 3, disconnects the dial tone, and at contact ErQ opens the locking circuit of relay 301', which removes the test potential from the contact engaged by brush 6 of theregister finder, thereby de-energizing relays T1" and SIM, Fig. 10. Relay E1, Fig. 10, however remains held via contacts U2 2 as already explained. At the end of the first impulse series, relay Ir relapses and closes a circuit for relay J1 via brush a of the thousands digit register. Relay Jr closes a'circuit for relay Gr via its contacts Jrl and parallel thereto a circuit for relay Kr via contacts GT2, F16, locks to contacts E11,

and at contact J13 transfers the impulsing.

circuit via contact Lr3 to ma net SW2 of the hundreds digit register. Rlay G1- is slowto-operate and before operating ensures the operation of relay Kr which locks up over contacts K1-3,Nr1, Erl. When the subscriber" Sends the'second series 'of impulses the magnet SW2 of the hundreds digitregister re sponds and the register takes up a position corresponding to the digit dialled. On the cessation of these impulses relay Lr becomes energized and transfers the impulsing circult to the magnet SW3 of the tens di 't register V18. contacts L74, S013, Or5. T 6 third series of impulses advances this register and when the last impulse is received relay Or energizes and transfers the impulsing circuit via contacts 014 to the magnet SW4 of the units digit register which resprrilnds to the last series of impulses.

en relay Kr operates at the end of the first di it it connects ground to the b wire of the undamental circuit via contact KM, winding of the outstepping relay Pr, contacts EM, and the register finder brush b, and connects battery to the a .wire of the fundamental circuit via a resistance, contacts K'r5 and the register finder brush a.

The connection of battery to the a wire closes a circuit for the common starting relay Acr, Fig. 7, of the first group finder control circuit via contacts 3174, 3Cr6 Fig. 3 and J 213, Fig.4 and places a potentlal on the contact of the level wiped over by brush '15 ixartlcular to the engaged second finder It will be convenient here to describe the arrangement of the bank contact of the group finder control circuit switches. These have 51 points or positions (the first being used as a home position) and five levels of contacts wiped over by brushes f The ten contacts in the first ten positions in levels It and i are wired to the ten first group finders controlled by the control circuit. The remaining 40 points in these two levels are not used. oints 11 to are used for reverting control and in levels 7 and g are divided into te n groups of four each. In level 9 the second and third contacts of each group of four are strapped together and grounded. The fourth contact of each group of four in level 7 as 14, 18, 22, etc. is wired to the marking terminals t of its corresponding group of junctions outgoing from the group finder switches. The marking wires are connected to terminals f1, f2, f3, etc., on a small terminal strip from which jumping wires are taken to. the group finders. The 100 out junctions, the normal capacity of the group finders, may be divided into ten groups of difierent-sizes, providing the total remains 100. The-d terminals of all the outjunctions of the first up are wired to the first terminal f1 in evel f of the control switch, all those ofthe second group to the second f terminal f2 and so on. All the junction groups may comprise 10 junctions each or some I groups may be larger and others smaller. As the group finders have no home o'sitions the junctions in. each group may be distributed in any order around the are so asto reduce hunting. Where ten junction ups are not required the finder arcs may divided into fewer groups. The contacts in'the level j are grounded and are used for centering the brushes.

g now the operation of thesystem, the start-relay A01, Fig. 7 when ener 'zed elem a circuit over contacts F012 and 011 for the power magnet PC and the control finder switch is rotated. A circuit is now closed over off-normal contact N for relay E01, Fig. 2, which prevents hunting of all the second line finders belonging to the suboup served by the control circuit. When t e predetermined group finder is reached, the test relay B01 operates to the battery on the test contact, the power magnet PC is disconnected andthe followin circuit is closed for relays For, Fig. 7, and i1, Fi 4 :batterg windings of relays F01 and 1'1, contact an wiper of level 71, contacts B0 2, E012, off-normal contacts N to ground. Relays For and J 1'1 lock to ound at contacts 3 B11, Fig. 3, via contacts 1'12, J 212 and the 0 wire and at contact J Z11 rela J11 connects the 11 wire of the fundamental circuit to relay D01 of the control circuit. Relay F01, Fig. 7 operates slowly and does not open its contacts F012 until relays Jz'r and D01 energize. The outstepping relay P1 in the register now energizes in series with relay D01, Fig. 7. Relay P1 closes at contact P11 a circuit via contacts M14 for relay R1, which closes a circuit for relay 1R1 over contacts R13 and wiper C of the first digit register providing that the switch is in one of the positions 1 to 9. This locking circuit is not closed if the switch is in position 10. Relay 1R1 closes a holdin circuit for relay R1 over its contact 1R11. Relay R1 closes an obvious circuit for relays N1 and S1 and at contact R15 connects the outstepping relay P1 in a metallic circuit across the a and 6 wires of the fundamental circuit. Relay B01 Fig. 7 now relapses being unable to operate in series with relay D01. Relay N1 opens the lockin circuit of relay K1 at contacts N11 and iolds over contacts S12, N12, E11. In the control circuit, relay D01 closes the following circuit for the powermagnet PC of the control finder switch :ground, off-normal contact N, contacts F011, D012, G014, winding of magnet PC to battery. The control switch now advances its brushes over theremainder circuit from ground at springs of ke RK via contacts Q12 and brush f of the t ousands digit register for the magnet SW1 thereof and locks up via contact Q11 and brush '0 i of this register .to the grounded interrupter contacts I of the magnet SW1, thus mamtaining the circuit of magnet SW1 closed even if relay P1 should open its back contact 1 before magnet SW1 is fully energized. In this manner the thousands digit re star is advanced until it reaches position 10 m which the circuit of relay IE1 is opened.- Relay 1R1 opens .the holding circuit of relay R1 so that at the next de-ener ation of the outsteppingRrelay P1, relay contact Relay S1 is now deprived of current and de energizes relay N1. Both these relays are of the slow-to-release ty and whilst'relay N1 is fallingawa the ollowing circuit is closed for relays 1 and Q1 ound contacts E11, N12, S11, brush 0 o thousands digit register, left-hand winding of rela M1 and winding of relay Q1 to battery. ela

Q1 recloses the circult of magnet SW1 whic advances the first register to its normal position whilst relay M1 recloses the fundamental circuit at contacts M15 and locks overits 1 relapses and at' 15 opens the fundamental circuit.

right-hand winding and contacts P11 of 1' cuit de-energizes and closes a circuit for relay G01 extending from ground at off-normal contacts N via contacts F011, D013 and G013. Relay G01 looks over contacts G012-3 and connects ground via'contacts G016, the high-resistance right-hand winding of test relay H01, brush f and the engaged marking terminal, to all the d terminals of the grou of junctions corresponding to the first digit dialled by the subscriber. The power magnet PJ, Fig. 4 of the group finder also receives ground over contact G015, H011 and J 113 and the group finder rotates. As its brushes 0 and t are connected together over front contacts J 115, when a free trunk in the wanted group extending to an idle second group finder the associated control circuit of which is also idle, is reached, the test relay H01 in the control circuit energizes from the bat- Scr and its own low-resistance left-hand winding parallel with .its high-resistance right-hand winding therebv busying the seized junction to other calls. Relay Smcloses a circuit via contacts Scrl and J Z14 for the group finder relay J2r which locks to the grounded front contact 3Br1 ofrelay 3Br,

1g. 3' in the link circuit. Relay Scr operates slowl to guard a ainst double connections. Re ay J2r comp ietes at contacts J21-4 and J2-r5 the through connect-ion from the line finder circuit to the seized junction and opens at contacts J2r2 the locking circuit of relay J 1r which releases thus disconnecting the group finder from the control circuit. Relay For is also deprived of current when relay J21 eneIC'gizes, opens the holding circuit for relay or and closes a restoring circuit for the control switch over the off-normal contact N and contacts F012 and Earl. If the relay Aer is energized due to another junction bein in a calling condition, the switch will continue rotating and the second junction will become immediately attached.

Returning now to the register,-when the relay Lr energizes after the recording of the second or hundreds digit. a furthercircuit is closed for relay Kr which extends from battery, contacts Fr6, right-hand winding of relay K1, contact Lr6, brush 1) of hundreds digit register, and contacts Mrl, Nrl, E'rl to ground. Relay Kr re-connects battery to the a wire and energizes the starting relay 8A0). Fig. 8 of the control circuit of the second group finder, and re-connects ground through the outstepping relay Pr to the 1) wire, -It will be seen therefore that if a second group finder is taken into use before the hundreds digit has been completely recorded, the-control circuit is not attached until the register is ready to' receive the reverting impulses. On the other hand if the register becomes ready to receive. the reverting impulses before a second group finder has been seized or before a control circuit has become attached to a seized second group finder, relay Kr will be re-energized immediately relay Mr relapses on the de-ene-rgization relay 1% when the fundamental circuit is opened on the first group finder engaging a free junction with the aid of its control circuit. and will therefore.- cause the attachment of a second group finder control circuit at the earliest possible moment.

A second group finder is shown in Fig. 5 and its control circuit in Fig.8 but since the operation of these circuits is similar to that of the circuits illustrated in Figs. 4 and 7 it is only necessary to describe briefly the operations at the second group selecting stage. The starting relay 8A0? closes a circuit for the control circuit driving magnet 8PC which advances the control switch wipers to the calling junction, on which magnet -SPC is tie-energized and the group finder relay 5J1'r energizes in series with the control circuit relay 8Fcr. Relay SE01 also operates and disconnects from the common lead to mark the control circuit and its associated second group finders non-selectable. Relay 5J1? attac ies the control circuit. The register outstepping relay Pr now energizes in series with the control circuit relay 8Dc-r over the Z wire of the fundamental circuit, the control switch is again rotated and revertive impulses are sent back to theregister circuit to count outthe hundreds register switch. The fundamental circuit is then momentarily opened at the re ister circuit, the control circuit relay SDcr de-energizing and energizing relay 8Gc'r, which connects up'the'test relay 81-101 and closes a circuit for the group finder power magnet 5PJ. The group finder hunts in the marked group and when a free junction is found relays 8H01', 8801' and 5Jcr energize. completing the connection to the final finder. Relay 5J2r opens the circuit of relay 5J11' which disconnects the control circuit. Relay 8Fcr relapses and closes a circuit for the magnet 8PC which drives the control switch to normal or to another calling junction. The fundamental circuit is opened and the register relays P1" and Mr de-energize.

Providing that the fourth or units digit register switch has moved to its firstposition, that is, that at least one unit impulse has been received by the register a circuit is again established for the relay 16' this circuit extending from battery, contacts F r6, right-hand winding of relay K1", brushes 6 of the units and tens registers, and contacts M1 1, N0 1, Erl, to ground. connects battery to the a wire of the fundamental circuit and ground to the 6 wire through the outstepping relayPr. The startmg relay 9.802 Fig. 9 of the fundamental circuit and energizes relay 913% which removes battery from the common lead to busy all the associated junctions as long as the common circuit is in use.

It will be convenient here to describe the arrangement of the bank contacts of the final control circuit switches. These switches have a capacity of 102 points arranged in two semicircular arcs of 51 points each. The finders have six sets of brushes as shown. The normal contact N closes whenever the switch leaves its home position and is not opened until the wipers have made a complete revolution' through 360. The lines in the upper and lower levels of a and f are numbered as indicated. The extra position H and H in each level is located where indicated.

The two levels 6 are used as described subsequently for P. B. X. hunting. These two levels are wiped over by two connected single- Relay K1- rements are wiped over by a double-ended brush twice during each complete revolution and the grounding of the fundamental circuit takes place over them. The segmentnmnediately preceding the positions H and H is one position longer than the others since the brushes have to take an extra step over these contacts to reach the beginning of the next group.

The levels h and a each contain 10 terminals occupying positions .1-10 in the first half revolution. These levels are wired to the final finder circuits, there being, therefore, capacity for 10 final finders in each group: This number however may be varied according to requirements. These levels are wi ed over by two single brushes and are there ore wi d over but once during a complete revolution of 360.

Level 7' consists of a series of rounded terminals wiped over by a dou le-ended brush. These terminals are used to centre the control finder brushes.

As the control finder may pick up a final finder between positions 1 to 10 it is necessary that the segment in positions 8 and 9 in level 9 be insulated until the brush c0m-' mences on its second half revolution. The reverting count is therefore commenced on the segment in positions 1820 and the con tacts in levels 6 and f are numbered accordingly. The first engagement of this segment by brush 9 causes the energization of relay 9Fcr, which grounds the first segment (in positions 89) during the remainder of the selective operation.

Resuming the circuit operation, relay 9Aar,

.Fig. 9 closes a circuit for the power magnet 91 C via contacts 9Acr1, 9D01'1, 9Fa1'7, and 9Bcr1. The brushes rotate and when the calling junction terminals are reached relay 9Bcr is energized over brush 2' and the a wire of the fundamental circuit, opens the circuit of the magnet 9PC and completes the following circuit :-ground, off-normal contacts N, contacts 9Dc1'1, 9F01-7 9Bcr2, brush h, winding .of relay F11, Fig. 6 and common lead to bat tery. Relay Flr ener 'zes looks over contacts F113, F3r5, F21 and the 0 wire to grounded contacts 5J21'1, Fig. 5 and closes a circuit over the 6 wire of the fundamental circuit for the outstepping relay Pr in the register circuit and for relay 9Dc1' in the control circuit. Relay 9Dcrrecloses the circuit in the bank 7'. When the brush g engages the first grounded group contact (positions 1820) ,a circuit is closed over contacts 9G01'5, 9Dcr3, 9Fcr2 for relay 9Fcr which .locks over contacts 9Fcr3 in parallel with relay Flr, Fig. 6 connects 'the brush 9 to the 6 wire of the fundamental circuit via contacts 9Gor5, 9D0r3, 9Fc1'1- and Flrl and grounds the first reverting group contact via contacts 9Ecr3and 9Fcr5. Aswill have been appreciated from the preceding description this contact occupies positions in the arc allotted to the calling 'unctions and the sending of reverting impu 5 must not be in until after the control switch has passe beyond this group in order that the-first reverting impulse shall always be sent back from the same position on the control switch are no matter 1 whether the first or last final finder is selected.

The control switch continues to rotate and for every ten steps a reverting impulse is sent over the 6 wire to count out the tens register in a similar manner to that previously described with reference to the thousands register.

When at the end of the last short-circuit impulse brush g leaves the grounded terminal the switch will sto on the next terminal f because the centering brush y will be connected to groundover a centering terminal before the brush 9 leaves the impulse contact.

In the register circuit when the tens register arrives in position 10, on the next relapse of relay Pr,\relay Rr falls away and opens the fundamental circuit. Relay Rr opens the circuit of relay Sr and between the relapse of the relays Sr and Nr the following circuit is closed :battery, winding of relay Qr, brushes 0 of the tens hundreds and thousands register, contacts Srl, N12, Erl to ground. Relay Qr steps the tens switch to its normal position. Relay K1 is immediately energized over its left-hand winding via brushes 6 of the tens and units registers, and contacts Mrl, N1'1, E'rl provided the last digit has been received and relay I'rhas relapsed and at contacts Ir2 removed the short circuit from the left hand winding of relay Kr. Relay Kr closes the fundamental circuit for the units selection and relay Pr causes the reoperation of relays Rr, 1R1, S1, N1". Relay Qr now relapses.

When the fundamental circuit is opened at the register circuit, relay 9Dar is de-energized, opens the circuit of the power magnet 9PC at contacts 9Dcr2 and closes a circuit via contacts 9D0r1, 9Fcr6 and 9Gcr2 for relays 9Gcr and Icr in parallel. Relay 9Gcr looks over contacts 9Gcr1, 9E0r3, and

for this being that when the units selectionis made the switch always makes one step. The contacts in level f of the control switch are connected -to contacts (1 in the banks of the final finders and when the final finder reaches the marked terminal (1 the following circuit is com leted for the test relay 9Hcr battery, win ing of 9Hcr, contact 9Gcr6, brush f of control switch terminal d and brush of final finder, contact F1r4 to ground. Relay 9Hcr opens the circuit of power magnet PF.

Meanwhile the fundamental circuit is reclosed at the register circuit and relay 9Dcr again energizes and closes a circuit for relay Ycr as follows :--battery, winding of relay Yer, contacts Ycr l, 9Gcr4, 9Dsr2, off-normal contact N to ground: Relay Ycr locks via contacts Ycr3, 9E0r3 and 9F01'5. Relay Ycr is made slow to energize in order to allow the stepping relay Pr in the register to energize and a helping relay Rr to energize over its front contact before relay Lcr energizes. Providing that the test relay Hcr has by this time energized a circuit is completed for relay Lcr via contacts 9H0r1, Mar? and Y0r2. Relay Lcr grounds the 6 wire of the fundamental circuit at contacts Lcrl and closes a circuit for the control switch power magnet 9P0 via contacts Lcr2, 9Hcr2, 9G0r7. Magnet 9PC advances theswitch and holds over the centering terminal on level 7'. When the brush on level f leaves the terminal on which it is standing relay 9Hcr relapses and opens the circuit of relay Lcr which removes the ground from the 6 wire of the fundamental circuit and recloses the circuit of the power magnet PF of the final finder which advances to its next position in which relays 9Hcr and Lcr again energize. In this manner reverting impulses for the units selection are sent back from the final control circuit to the register circuit, the final finder making one step for each impulse.

In the register circuit the revertin impulses are repeated as before by relay r to the units register magnet SW4. In position 10 of this register switch, relay Rr is unlocked on the next relapse of relay Pr. Relays Sr and Nr are de-energized and before relay Nr has time to relapse a circuit is closed for relay Dr via brushes 6 of all the re 'ster switches and contacts Srl, Nr2, Erl. elay Dr locks up over contact Dr l and opens at contacts Dr3 the circuit of relay Ur. Relay UR opens the lockng circuit of relay Er which in turn unlocks all the operated relays in the register circuit excepting relay Dr. Relay Dr also closes a circuit for relay Qr via contact Dr5, brushes e of 'all the registers and nterrupter contacts of magnet SW4.

Relay Qr closes a circuit to step the units re is'ter intov its normal position. Relay 1' releases immediately the units register steps out of position 10, but in the normal position IS again energized ov'er contacts Dr5, the brushes e of the registers and contacts D14. A check is made that all the register switches are at normal and 1a circuit is then closed via contacts QrQ'and all the brushes f for short circulting relay Dr. An exchange attendant by throwing kcy RK can close a circuit for relay Dr to restore the register circuit. Progress lamps 1L, 2L, 3L are lighted in parallel over the locking circuits of relays Jr, Lr, Or

and lamp 4L over the off-normal bank a of 'the units register to indicate the progress of the setting of the register circuit.

Returning now to the final control circuit when the register is counted'out the-fundamental clrcuit is finally opened in the register c1rcuit relay 9Dcr deenergizes and the following circuit is closed for relay Mcr: battery, winding of relay Mar, contacts Mcr5, Ycr5, 9Fcr6, 9Dcr1, off normal contacts N to ground. Relay Mcr'locks up via contacts Marti, 9Ecr3, 9Fcr5, disconnects relay Lcr, at contacts Mcr3 before it has time to operate again, at contact Mcr4 closes a circuit for relay Xcr via contacts Perl, 9Hcr1 and in parallel thereto via contacts 1012 for slow-release rela J or. Relay Xcr locks over contacts Xcr l, 9 *cr3, 9Fcr5 and at contacts X01 2 connects ground via contacts F1r6 to the test relay Ftr F i 6 and at contacts Xcr6 opens the circuit of relay Icr which commences to release and on closing its contact Icrl'opens the circuit of slow-release relay J or and short-circuits the winding of relay Ycr over contacts Mcr4 and 9Hcrl. Relay Yer releases. At the moment of testing a holding ground is given to relay Flr, Fig. 6 via contacts 9D0r1, 9F cr6, Xcr5, J crl, 9Gcr6, control switch brush f, final finder brush d, and contacts F1r4. With relay Ycr de-energized and relay Xcr energized a ground is connected to the winding of relay F 3r, Fi 6 via contacts Ycrl, Xcrl, F1r5. Relay F3r operates and looks over contact F3r3, Frrl. The relapse of relay J or after an interval opens the holding circuit of relay Flr which frees the control circuit. It is arranged that the release period of relays Icr and J or is sufiicient to allow time for testing.

If the wanted line is idle, relay Ftr energizes in series with the cut-off relay thereof line, contacts F2r4, F3rl to ground. Telltale ringing tone is applied to the callingline through the condenser MFR. When the called party answers, relay Frr operates and unlocks relay F3r. The called party is now connected through to the link circuit, Fig. 3

where relay 3Csr energizes over the called partys loop and closes a circuit for relay 3Fr to ground at the contacts 3Br1, via its con-' relay F31, busy tone from the source ET is' transmitted to the calling line via contacts F211, F312 and the condenser MFR.

When the holding circuit of relay Flr is opened this'relay relapses and disconnects the control circuit. The relapse of relay 9Fcr de-energizes relays 9Gor, 9Her, Xer and Mar, and a restoring circuit for the magnet 9PC is closed over elf-normal contacts N, contacts 9Dc1'1, 9Fc'r7 and 9B01'1. If the called party hangs up but not the calling party, relay 3Cs1' relapses and circuit 3Br1, 3Csr2, 3Fr3 is closed for a lamp GL over an alarm wire.

When the calling arty hangs up relay 3Asr de-energizes and opens the circuits of relays 3D1', 3H1; and 3B1: Relays 3Br and 3H1 release slowly. Metering battery is connected to the e wlre via contacts 3Fr2, 3H7'l to operate the service meter SN, Fig. 1. When relay 3B9 releases, relay 3F1' de-energizes and disconnects the metering battery. Relay 3B1 removes ground from the forward 0 wire causing the relapse in turn of the switching relays J27, Fig. 4, 5H2r, Fig. 5 and F273 Fig. 6 at the group and final finders. These switches remain on the junction or line terminals with which they are in engagement. The opening of the 0 wire thus makes the connection instantly available for a second connection.

Private branch exchange hunting The level e of the final control finder is used for P. B. X. hunting and the front contacts COTQ, Fig. 6 of the cut-off relays on all lines in a P. B. X. group except the last are connected to terminals on this level. When the units selection is completed and relay M01- energizes, a circuit is prepared over contacts Mer7, X07 3 for relay Per. Relay For operates faster than relay Xcr which is slowto-operate and if the wanted number is one of a P. B. X. group and is engaged relay Par energizes over brush e and contacts (101-2, opens the circuit of relay Xcr at contacts Perl, and closes a circuit over contacts P012 for the power magnet 9P0 which advances the control switch a step on the next contact set where relay 9I-Icr falls off and closes the I circuit for ad\-'a.n('in r the final finder to the tion is continued until either a free line in the group is found or the last line is reached. On the last line the front contact of the cutofi' relay is not connected to the 0 level and hunting is therefore definitely stopped. The

last line is tested in exactly the same way as a single line and if it is engaged the busy tone is'given to the calling party.

- Special service calls As previously stated the register circuit is arran ed to handle two digit special service calls for which the numbers 01, 02 etc., are reserved. If a first digit 0 is dialled the thousands register switch is stepped to position 10 and on the response of relay J r a circuit is closed via contacts D1'3, brush 1) and contacts G-r1 for relay S01" which looks over contacts Sm t-5 to ground at contact Jrl. Over contacts Serl and S02 8 the connections to the tens register are opened, whilst at contacts Ser6-7 the 10th terminal of the 0 bank of the hundreds register is transferred from relay Mr to relay Dr. At the end of the second digit relay L1- is energized as in a normal call. The register circuit now controls selection at two group finder stages, at the end of the'second selection relay Dr being energized instead of relay Mr over the following circuit :-ground, contacts Erl, N12 and Srl, brushes 0 of thousands and hundreds register switches, contacts SW6, winding of relay Dr to battery. The energization of relay Dr causes the register circuit to be released as previously described.

The call is directed over a regular first group finder such as that shown in Fig. 4; and a special service second group finder to local trunk to an op'erators position. The special service second group finder differs from a regular secondgroup finder in that a fifth brush is provided: lts operation is identical. When a special service trunk is engaged a calling relay at the operators position is energized over the 0 wire and lights a calling lamp. The operator plugs in, the connection of earth to the sleeve contact closing a circuit over the d wipers of the special service second group finder and the regular first group finder, and relays 3131* and 3G1 at the link circuit, Fig. 3. Relay 3Gr opens at contacts 3Gr4 the circuit of the relay 3Dr which disconnects the calling side current bridge. Relay 3E7' disconnects the called side current bridge. The calling subscriber is now connected to the operators position over a metallic circuit including contacts 3Grl, 3Gr2. The cut-off relay of the calling line is Ill) 4 release control to the operator. If the operator should release before the calling subscriber relay 3Gr de-energizes and the circuit of realy 3Dr is again closed and the current bridge connected to the calling line. Relay 3Asr therefore energizes and closes the original circuit for relay 3Br which holds the connection.

Premature releases Premature releases are characterized by the opening ofthe loop to relay 3Asr, Fi 3 and the subsequent relapse of relays 3 r, 3Dr. The connection to the 0 brush of the register finder is thereby opened causing the deenergization of relay Ur, Fig. 10, in the register circuit and the completion of -a circuit for relay Dr via contacts Ur3, Gr4. Relay Dr locks over its contact Dr4 and initiates the restoration of all the register switches which are out of normal, by closing the following circuit for relay Qrz-ground, interrupter contacts I ofmagnet SW1, ofi-normal arc and brush 6 of the thousands register, contacts Dr5 and winding of relay Qr to battery. Relay Qr at cont-acts Qr2 connects ground of the brush f of the thousands register which goes home. In the home position the thousands register a similar homing circuit 1s closed for the hundreds regiser and so on until all the registers are restored and relay Dr is short-circuited over contacts Qr2 and the brushes f of all the registers in their home positions. When relay Dr relapses relay (Jr is de-energized and the register circuit fully restored.

' When relay 3Br, Fig. 3 relaspes, ground is removed from the forward 0 wire causing the freeing of the conversation finders which may have been taken into use.

All tram/ts busy It will be remembered that relay Mr in the register circuit energizes and locks over the front contacts of-relay Pr when a group finder commences its hunt for an idle trunk in a wanted group and is unlocked when the relay Pr de-energizes on the opening of the fundamental circuit when an idle trunk is seized. Relay Nr is de-energized at this time. Relay Mr at contacts Mrl holds open the circuit of relay Kr and in this condition a circuit is closed for the driving magnet TA of the time switch T via contacts K1 2, Nrl, Erl. If after a predetermined interval, say 10 seconds, an idle trunk has not been picked up and the relay Mr unlocked and relay Kr again operated, when the brush 2 of the switch T engages contact 1 a circuit is closed via contact Mr2 for relay Fr which locks to grounded contacts Erl. Relay Fr connects busy tone over lead B and contacts Fr3 to the primary of the tone transformer TC in place of dial tone, unlocks relay Mr at contacts Fr6, and by opening contac s Frl introduces the high resistance winding of relay Ur in the circuit of relays Ur, Fig. 10 and Er, Fig. 3. Relay Er, Fig. 3 now falls away and busy tone is sent to the calling party over the cir-- cuit previously described with reference to the transmission of dial tone. When the subscriber replaces his receiver the register circuit and the talking circuit switches are released as in a premature call. If after the expiry of a predetermined interval the register is not released when the brush 2 of the switch T engages contact 5 an alarm lamp GL is lighted.

During the hunting for a free trunk by a group finder, Fig. 4 or Fig. 5, relay DCr, Fig. 7 or 8Dcr, Fig. 8 of the associated control circuit is maintained operated from the register circuit, but on the expiry of the 10 seconds, when relay Mr is unlocked, relay Dcr or 8Dcr is released and closes a circuit for an alarm lamp AL over contacts Gcrl, D0r3, Fcrl (or 8Gcrl, 8D0r3, 8Fcrl).

False calls If a bad line creates a call, when a register circuit is attached, on the energization of relay ,Er, Fig. 10 the following circuit is completed for the driving magnet TA of the timing switch T :ground, contacts Erl, Nrl, Kr2, winding of magnet TA to battery. Atter the expiration of a predetermined interval of say 30 seconds the timing switch T advances its wiper 2 to the contact 4 and closes a circuit for relay Xr via contacts Gr5. Relay Xr closes a circuit for the magnet SW1 of the thousands register via interrupter contacts I, contacts Jr6, Xrl, brush 7, contacts Xr3. The thousands register continues to step over a circuit including strapped contacts 2 to 9 of arc f until it reaches position 10 where its circuit is opened, relay Jr energizes over the brush a and relay Scr energizes over the brush 6, locks to contacts J r1 and maintains the circuit of relay Xr over contact-s $072. A holding circuit for the time switch magnet TA is also closed via contacts Jrl, Scr5, Lr7 wiperl of switch T and contact 3. A circuit is now closed for the magnet SW2 of the hundreds register extending In the meantime rela Kr has become energized over contacts 9 2, Jrl, and selection proceeds as if the digits 00 had been dialled and take place in exactly the same way as a special service connection. The subscribers line is thereby extended over one of a special group of junctions to a false call position, Fig. 11 where relay 4Br is energized and lights the calling lamp SL. Relay 4A1' is energized over the brushes (1 of the first and second group finders in series withrelay 3E1 and 3G)", Fig. 3 in the link circuit. Relay 4A1 locks to the 0 wire. Relays 3E? and 361', Fig. 3 remove the current bridges at the line finder circuit as in a special service call and the calling line is metallically connected to the false call circuit, battery and ground being supplied through the windings of relay 4B).

\Vhen the false call operator inserts a plug PF in the jack F J relay 4C1' energizes over the sleeve wire and disconnects relay 4137. The subscribers line is now metallically connected to the false call operators cord and can be tested for insulation etc. To enable faulty lines to be traced back and plugged out the lamp GL, Fig. 3 can be flashed from the false call position. For th1s purpose a key FCK is provided which when depressed opens the circuit of relays 3E?" and 3G1, F10. 2. The operator then depresses a key FR which bridges the talkin Wires causing the energization of relay 3613, F 1g. 3 whlch closes the circuit of relay 3F'r: relay 3F? locks up independently of relay 3C81". When the kev FK is subsequently vibrated relay 3087' is intermittently energized and flashes the lamp GL. When the line finder circuit has been located, the key F CK is released and the metallic through connection agamestablishcd. Relay 3Fr, Fig. 3 is unlocked so that if the fault is cleared the meter Will not be operated. The register circuit 18 restored in the usual manner.

Claims.

1. In a telephone exchange system, the combination of a plurality of single-motion power driven conversation switches, a plurality of control switches common to said conversation switches, means under the control of said control switches for controlling the operation of said conversation switches, a register controller, means under the control of said register controller for controlhng the operation of said control switches, and means under control of said control swltches for transmitting revertive impulses to said register controller.

2. In a telephone exchange system, the combination of a plurality of switching stages, a plurality of single-motion power driven conversation switches at each switching stage, control switches each common to a plurality of conversation switches but individual to the switching stage to which said conversation switches belong, means under the control of a control switch to control the operation of the conversation switches, a register controller, and means under control of said control switch for transmitting revertive impulses to said register controller.

3. In a telephone exchange system, the combination of a group of conversation switches, a control switch common to the group of conversat on switches for controlling their operation, a common registering and controlling mechanism for registering a wanted number, and means under control of said control switch to transmit revertive im' pulses to said registering and controlling mechanism to control the operation of said control switch.

4. In a telephone exchange system, the combination of a plurality of switching stages, conversation switches at each switching stage, control switches, means under control of said control switches for directively operating said conversation switches, regis- .tering and controlling mechanism for recording a wanted number, and means under control of said control switches to transmit revertive impulses to the registering and controlling mechanism at the respective switching stages.

5. A telephone system comprising a plurality of selectors, control switches, common to said selectors, and provided with brushes which are adapted to move in the same direction, first to select groups of lines and then a line within a selected group, a regis- 1 tering and controlling mechanism, and means under control of said control switches for sending revertive impulses to said registering and controlling mechanism over their brushes during their movement.

6. A telephone system comprising a plurality of selectors, .control switches, common to said selectors, and provided with brushes which are adapted to move in the same direction, first to select groups of lines and then a line within a selected group, a registering and controlling mechanism, and means controlled by said control switches for sending revertive impulses over their brushes during the first selecting movement, and a second set of revertive impulses during the second setrolling mechanism.

7. A telephone system comprising a plurality of selectors, control switches, common to lecting'movement to said registering and consaid selectors, and provided with brushes i which are adapted to move in the same direction, first to select groups of linesand then a line within a selected group, a registering and controlling mechanism, and means controlled by said control switches for sending revertive impulses over their brushes during the first selecting movement, and a second set of revertive impulses during the second selecting movement, the means under the control of said control switches for transmitting said revertive impulses comprising a relay, the operation of which transmits impulses to said registering and controlling mechanism.

8. In a telephone exchange system, the combination of a plurality of switching stages, a plurality of conversation switches at each switching stage, a control switch common to a plurality of conversation switches, a registering and controlling mechanism, and means under control of said registering and controlling mechanism to control the operations of the control switch at two or more switching stages.

9. In a telephone exchange system, the combination of a plurality of conversation switches, a control switch connected in permanent multiple relation with said plurality of conversation switches, a relay individual to each conversation switch, and means for operating the relay of any conversation switch whereby said control switch is connected with a conversation switch by its operated relay.

10. In a telephone exchange system, the combination of a. plurality of conversation switches, a control switch common to said conversation switches, a relay individual to each conversation switch, and means for operating the relay of any conversation switch whereby the control switch is operatively associated with said conversation switch.

11. In a telephone exchange system, the combination of a group of conversation switches, connected with groups of lines, a control switch, means for predeterminedly operating one of said conversation switches, means for associating said control switch with the predetermined conversation switch,

means for then advancing said control switch, registering and controllingmechanism, means controlled by said mechanism for controlling the advance of said control switch, and means controlled by said control switch when it advances to apply a marking potential to a wanted line or group of lines in said conversation switches, said control switch in its advance serving to send revertive impulses to said register mechanism;

12. In a telephone exchange system, the combination of a plurality of conversation switches, a control switch common to said conversation switches, means for advancing said control switch to a particular position in two selecting movements, a registering and controlling mechanism, a loop circuit extending from said control switch to said registering and controlling mechanism, and means controlled by said control switch in its selec tive movements to send'revertive impulses to said registering and controlling mechanism by grounding one side of said loop circuit.

, 13. In a telephone exchange system, the combination, of a plurality of conversation switches, a control switch common to said conversation switches, means for advancing said control switch to a particular position in two selecting movements, aregistering and controlling mechanism, a loop circuit extending from said control switch to said registering and controlling mechanism, and means controlled by said control switch in its solective movements to send revertive impulses to said registering and controlling mechanism by grounding one side of said loop circuit, and means in said registering and controlling mechanism for opening said loop circuit to stop the movement of said control switch.

14. In a telephone exchange system, the combination of a plurality of conversation switches, a control switch common to said conversation switches, means for advancing said control switch to a particular position in two selecting movements, a registering and controlling mechanism, and means under control of said control switch for sending a set of reverting impulses to said registering and controlling mechanism during each of said selecting movements.

15. In a telephone exchange system, the combination of a plurality of conversation switches, a control circuit and an auxiliary switch, and means for causing said auxiliary switch to associate said control circuit with the conversation switch and also to control the advance of'said conversation switch to a wanted position.

16. In a telephone exchange system, the combination of a plurality of conversation switches having sets of contacts, a common control circuit connected in multiple relation to said conversation switches, a switching device individual to each conversation switch for connecting its associated conversation switch with said common control circuit, an auxiliary switch associated with said common control circuit, and, means for causing said auxiliary switch to first hunt for a contact set particular to a conversation switch and then causing the operation of the switching device individual to said conversation switch and then to subsequently advance to a further position to another set of contacts in the bank of said conversation switch.

17. In a telephone exchange system, the combination of a plurality of conversation switches having groups of outlets, a control circuit common to a plurality of said con-- versation switches, an auxiliary switch associated with said control circuit, and means for first causing said auxiliary switch to advance to certain positions to cause said control circuit to become associated with a conversation switch, andthen advance a second time to control the advance of the conversation switch to a wanted group of outlets.

18. In a telephone exchange system, the combination of a plurality of conversation switches having groups of outlets, a control circuit common to a plurality of said conver- 

